BRCA1/2 mutation carriers have highly elevated odds of developing hereditary breast and ovarian cancer, as may their first- and second-degree relatives. The National Academies of Sciences Engineering and Medicine?s Genomics and Population Health Action Collaborative highlights the testing of carriers? relatives and their uptake of screening and risk-reducing surgeries as a primary way that genetics can contribute to the reduction of population cancer burden. Patterns of testing over the past decade have shifted to include more younger and cancer-unaffected women to capitalize on this cancer prevention opportunity. However, interventions have not kept pace with this changing landscape, as there are currently no funded trials that meet the unique clinical, developmental and psychological needs of young adult relatives (YARs) of mutation carriers. Our pilot data suggests that YARs report high levels of distress and desire to seek HBOC risk information and emotional support beyond their healthcare providers and families?especially support from knowledgeable peers who can relate to their experiences and offer neutral grounding and objective guidance about coping strategies. Peer support is a promising psychosocial cancer care approach that could fill this void. However, few evidence-based standards inform its practice. In response to this cancer control challenge, we developed a new, fully manualized/scripted intervention for YARs called ?Peers and Cancer Empowerment? (PeACE). PeACE is grounded in evidence-based psychosocial telephone counseling protocols for HBOC distress reduction. We adapted those protocols for our target population through a systematic approach without contradicting their core features. PeACE includes streamlined telephone counseling delivered by well-trained community peer coaches. Session content incorporates coping training for HBOC stress reduction, and decision making and problem solving training about confronting and managing cancer risk. We will rigorously test PeACE?s efficacy in an RCT to improve HBOC-related outcomes for YARs. Trial participants are randomized to an intervention or equated control condition, and followed for up to 12 months. We hypothesize that PeACE better reduces cancer-specific and general distress, uncertainty, and decision conflict, as well as increased uptake of genetic counseling. This innovative project expands capacity to address psychological distress management and related outcomes in persons living with HBOC risk.